Brassinin Induces H₂S Signals and Improves Vascular Smooth Muscle Cell Functions

Brassinin, a sulfur-containing phytoalexin, exerts anticancer and anti-inflammatory effects. Hydrogen sulfide (H₂S) is an important gasotransmitter with significant cardioprotective properties. The effects of brassinin on H₂S signaling and vascular smooth muscle cell (SMC) functions remain unexplored. This study found that brassinin protected against angiotensin II (Ang II)-induced SMC dysfunctions. These effects included the attenuation of excessive cell proliferation, migration, and oxidative stress; and upregulation of smooth muscle contractile protein expressions; and down-regulation of inflammatory gene expressions. Notably, brassinin did not directly release H₂S under the tested conditions; instead, it stimulated endogenous H₂S synthesis in cultured SMCs by inducing the expression of cystathionine gamma-lyase (CSE), a key H₂S-generating enzyme. Further mechanistic investigations revealed that brassinin may bind to the transcription factor C/EBPβ and enhance its interaction with the CSE promoter, thereby upregulating CSE transcription. In conclusion, our findings demonstrate that brassinin protects against SMC dysfunction, at least in part, by activating H₂S signaling rather than acting as a direct H₂S donor. These results provide new insights into the potential of brassinin as a therapeutic agent for improving vascular health and preventing cardiovascular diseases.